The use of vortex generators for reduction of tendency to separation of the air flow on aircraft wings has long been well-known in the art, and an example is given in U.S. Pat. No. 4,354,648 disclosing a aircraft wing having two or three rows of low-profile vortex generators extending from the suction side surface e.g. 10-20% of the thickness of the boundary layer.
Application of vortex generators on wind turbine blades is also well known in the art. The use of vortex generators on wind turbine blades to counteract flow separation and stall is disclosed in WO 00/15961 (LM Glasfiber) showing the use of vortex generators along the whole span of the blade or at the tip end thereof, the vortex generators being of a generally triangular shape and extending from the suction side of the blades to a height of 0.01 to 10%, preferably 0.25 to 6% of the chord length.
Also in WO 01/16482 (Stichting) wind turbine blades provided with vortex generators on the suction side and/or on the pressure side are disclosed. The preferred height of the vortex generators is disclosed as about 1% of the chord length and the purpose of the vortex generators is to prevent the occurrence of sudden stall during gusts of wind causing loss of production and vibrations.
In WO 2006/122547 (Vestas) yet another disclosure is made of wind turbine blades with vortex generators, in this case for a pitch controlled wind turbine, with the purpose of reducing the emission of noise during stall. The height of the vortex generators is disclosed to be between 0.01% and 5% of the chord length.
Thus, the provision of vortex generators, including micro vortex generators to wind turbine blades is well known in the art with the purpose of reducing noise emission and preventing stall as well as making the occurrence of stall more gentle and predictable. The fact that vortex generators increases the drag coefficient of the blade and thus reduces the power production of the wind turbine delimits the actual use of vortex generators on wind turbine blades.